You can download the entire OSM data catalogue and host it in your servers.
I feel like when saying this, you have to mention that it is(or at least was when I was tasked to do so 2 years ago) notoriously crazy to host an OSM tile/nominatim server for a mid-size country, and even more so for the entire world.
Requires some dedication and lots and lots of disk space and bandwidth - probably most feasible in a box at home with only you yourself having access and not having to pay monthly for high-traffic storage.
I think an easy to setup self-hosted vector/tile server could help increase adoption. I'am currently looking into replacing Mapbox with a self hosted solution. My last attempt ran out of disk space building the docker images (with european maps) from https://github.com/Overv/openstreetmap-tile-server. Haven't found the time to setup a larger VPS but this looks like a great project to get started.